Shipyard describes this as a nontraditional English bitter ale. It's closest to the extra special bitter, or ESB, style, which is bigger and hoppier than the usual English bitter. (Of course, neither is anywhere near as hoppy as a West Coast India pale ale, because nothing is.)
One thing that might make Old Thumper nontraditional is the inclusion of some roasted malts, which gives a fleeting suggestion of a darker beer. Because Shipyard has been making this beer for more than 15 years, though, by American standards it is a tradition.
It pours amber with a pale yellowish head and a mild nose of fruits — apples and maybe bananas, rather than the usual West Coast citrus effect. The English hops give it a crisp attack on the tongue, but the palate is slightly more malty-sweet than bitter. A little more bitterness shows up about halfway through the finish. This is basically a beer for drinking by itself, but it's comfortable with pizza and stuff from the grill.
— Charles Perry